In evaporators for motor vehicle air conditioners, it has heretofore been practice to arrange inner fins in flat tubes to give an increased heat transfer area to the refrigerant and thereby achieve improved performance.
Already known as such an inner fin is one comprising a metal sheet of corrugated cross section and enclosed in a flat tube. The inner fin has all ridges and furrows thereof brazed to the inner surface of the flat tube.
The inner fin described has been given an increased heat transfer area by diminishing the spacing between the ridges and the furrows, i.e., the fin pitch, whereas difficulties are encountered in fabricating inner fins having a further decreased fin pitch. It has also been found that if realized, further diminished fin pitches are unable to achieve correspondingly improved effects.
An object of the present invention is to provide an inner fin for heat exchanger flat tubes which comprises a metal sheet of corrugated cross section and which is adapted to achieve a further improved heat transfer efficiency without diminishing the fin pitch. Another object of the invention is to provide an evaporator wherein the above inner fin is used and which is thereby improved in performance.